The invention relates in general to wireless communication systems and in particular to wireless local and wide area networks.
There was a time when mainframe computers ruled the workplace. The mainframe was a single high-powered computer located at a central site. Users worked on dummy terminals (i.e., displays and keyboards), which were connected to the mainframe. All programs and all data were stored in the mainframe, and all computations were performed by the mainframe. On mainframes such as the DEC VAX, processor time was allocated to the users based on priority. Low priority users had to share the processor time, while high priority users worked in real-time, monopolizing the processor time until their jobs were completed. Delays resulted from heavy usage among low priority users and from high priority users whose jobs were lengthy. Additionally, mainframes were expensive to purchase and expensive to maintain, requiring a cooled environment and at least one full-time operator.
Then came personal computers, workstations and networks, which ended the reign of the mainframes. Personal computers and workstations contained their own processors, allowing the users to work in real time. Networks allowed the personal computers to share information among each other. They also allowed expensive hardware (e.g., printers) and software to be located at one personal computer (a server) and shared among the other personal computers (clients). The networks were also affordable. It made economic sense for large companies to replace the expensive mainframes with networks of personal computers and workstations. Not only were the networks affordable for large companies, they were affordable for small companies and offices that previously could not afford or justify mainframes. Today, mainframe computers are still in use, but primarily as storage devices. Personal computers, workstations and networks now rule the workplace.
The networks can be classified as local area networks (LANs) and wide area networks (WANs). WANs and LANs differ in several aspects. WANs operate over public networks (i.e., leased lines furnished by third paries such as telephone companies), whereas LANs operate over private networks (i.e., privately owned cables and components). WANs transmit data at rates on the order of thousands of bits per second, whereas LANs transmit data at rates on the order of millions of bits per second. WANs are more error prone because they cover large outdoor geographical areas. Bit Error Rates are on the order of 1 in 105 bits transmitted. LANs, which are typically housed within buildings, have Bit Error Rates on the order of 1 in 109 bits transmitted.
The concept of networking is evolving from wired networks to wireless networks. In a wired network, a signal flows from one device to another across a physical medium such as copper wire or and fiber optic. In a wireless network, a signal flows over the airwaves at a radio frequency. Devices in a wireless network are untethered; unlike the devices in a wired network, they can be moved freely and can tap into a source of information anytime, anywhere. The wireless network also eliminates two unbecoming aspects of wired networks: the unsightliness of cables, and the expense of cable installation.
However, the success of the wireless network will ultimately rest upon its ability to handle large amounts of information in real time. Nowadays, networked computers are being used for the communication of divergent types of information including computer coded graphics and text, audio and video. The information could come in large volumes of data from commercial databases and electronic mail. The information could come in the form of real time video and audio, as required for video conferencing. The information could come from computers that share computer power in multiprocessor multitasking environments, where highly parallel computing is performed with all available computers on a network system. In the future, computers will be faster, and real time information will be needed in even larger volumes.
Wireless networks operating at RF frequencies are presently unable to handle the large amount of information, even by the current standards. When the quantity of information on the network becomes excessively high, the quality of the channel deteriorates. Also, the heavy xe2x80x9ctrafficxe2x80x9d increases the transmission errors, thus inversely reducing the xe2x80x9cthroughput,xe2x80x9d the amount of information that can be actually communicated on a channel. Because high error rates are unacceptable, the transmission rates must be lowered in order to decrease the errors. Effectively, the bandwidth of the network is reduced.
It is an object of the present invention to increase the effective bandwidth of a wireless network.
According to a broad aspect of the present invention, a wireless network comprises a plurality of devices, each of which has at least one transceiver operable over an RF bandwidth. The network further comprises at least one interface that allows the plurality of devices to communicate with each other. The RF bandwidth is dynamically allocated among the devices by the at least one interface. Units of the bandwidth are apportioned among the devices according to the requirements of the devices.
One embodiment of the wireless network according to the present invention is a Time Division Multiple Access network. Another embodiment is a wireless Ethernet. Yet another embodiment is a Frequency Division Multiplexed network.